p-Toluenesulfonic acid → trans 4-(Bromomethyl)-2-methoxy-1,3-dioxolane

関与物質

反応手順

To a solution of 3-bromo-1,2-propanediol (6.0 g, 38.7 mmol) in benzene (90 mL) was added trimethylorthoformate (4.23 mL, 38.7 mmol, 1 eq.) and p-toluenesulfonic acid (pTSA, few crystals). The mixture was stirred for 20 hr at 85°-90° C., then cooled to room temperature and benzene was removed under reduced pressure. The crude material was obtained in 96% yield (7.26 g) as a mixture of cis and trans isomers in a 1:1 ratio. 1H NMR (300 MHz, CDCl3) δ: 3.34 and 3.35 (2s, 3H, OCH3), 3.35 (m, 1H, CHAHBBr), 3.44 and 3.58 (dd, 0.5H, J=5.0 Hz, 15.0 Hz, and dd, 0.5H, J=5.0 Hz, 9.9 Hz, CHAHB Br), 3.92 (dd, 0.5H, J=8.3 Hz, 10.7 Hz, and d, 0.5H, J=8.2 Hz, H-5a), 4.21 (dd, 0.5H, J=6.9 Hz, 15.0 Hz, and d, 0.5H, J=8.3 Hz, H-5b), 4.45 and 4.55 (2m, 1H, H-4), 5.80 and 5.82 (2s, 1H, H-2).

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